World's First Electronic AWG -The Photoformer

[Fred Bloggs]

Just make a cutout of the arbitrary function from opaque material and
tape it to the CRT, photoamp servos the vertical sweep to cutout contour :
View in a fixed-width font such as Courier.

 

[John Larkin]

Just make a cutout of the arbitrary function from opaque material and
tape it to the CRT, photoamp servos the vertical sweep to cutout contour :
View in a fixed-width font such as Courier.

.
.
.
. ---------------------
. / |
. / |
. / |
. / | lightproof enclosure
. oscilloscope / ----------------------------
. / / |
. / / |
. / / / \ |
. / / / | | | | |
. ---------- / / / -~~~~~~-> | | | photodetctor |
. | | | | | | | | amp & ps |
. | | |/ / ----- |
. | | | / | | |
. | | |/ | | |
. | | ----- |
. | | | | |
. | ---------------|-|----------------
. | | | |
. | y | | |
. | o------- |
. | o---------
. | /
. | x /
. | o-------< sweep
. | o-------< in
. | /
. | /
. | /
. | /
. | /
. ------------- /
.
.
.
.

I did this when I was a teenager, early 60's, with a pmt and my
Knight-Kit DC-coupled scope. In retrospect, it's surprising that the
loop was stable.

Any idea when this was first done?

John

 

[Fred Bloggs]

I did this when I was a teenager, early 60's, with a pmt and my
Knight-Kit DC-coupled scope. In retrospect, it's surprising that the
loop was stable.

Any idea when this was first done?

John

Are you telling us you conceived and built this independently?

 

[Fred Bloggs]

I did this when I was a teenager, early 60's, with a pmt and my
Knight-Kit DC-coupled scope. In retrospect, it's surprising that the
loop was stable.

Any idea when this was first done?

John

It almost certainly goes back to the 40's, or whenever analog computers
first were seriously relied upon to solve scientific analysis problems.

 

[Spehro Pefhany]

It almost certainly goes back to the 40's, or whenever analog computers
first were seriously relied upon to solve scientific analysis problems.

I remember this trick from way back (can't remember the source, but I
didn't think of it myself)... it's really just the electronic analog
of a mechanical cam follower, which would date back at least to
sometime in the industrial revolution.


Best regards,
Spehro Pefhany

 

[John Larkin]

Are you telling us you conceived and built this independently?

Yup. I was building a light-beam radar (surplus military xenon
flashtube, 931A pmt, crude optics) and just for grins aimed the pmt at
the face of the scope. At the right distance and gain settings, it
traced the curvature of the tube. So then I stuck my hand in the
way...

It's cool, the way the beam will ride up the slope of your finger,
then fall off. Lots of people must have done this by accident... once
you've got a pmt connected to a scope, it's pretty obvious.

I invented the dual-slope integrating ADC about that same time, but
forgot to patent it. I figured that as long as I used relays to do the
analog switching (that's what I imagined) it wouldn't be very
accurate.

John

 

[Luhan]

Just make a cutout of the arbitrary function from opaque material and
tape it to the CRT, photoamp servos the vertical sweep to cutout contour :

Hey, this looks a lot like the famous 'flying spot scanner'. Put an
object between a TV with a white raser and a phototube. It was used by
TV technicians to generate a standard test pattern by using a
transparent image in the middle. All in a box, you inserted a
selection of transparencies for different test patterns.

Luhan